Argument Fowarding Tests should account for newline added by StreamFowarder. Add an entry to developer guide so command developers will use Console.WriteLine. PR feedback and slight refactoring.

test/ArgumentForwardingTests/ArgumentForwardingTests/ArgumentForwardingTests.cs

@@ -206,7 +206,7 @@ namespace Microsoft.DotNet.Tests.ArgumentForwarding
         /// <returns></returns>
         private string[] ParseReflectorOutput(string reflectorOutput)
         {
-            return reflectorOutput.Split(',');
+            return reflectorOutput.TrimEnd('\r', '\n').Split(',');
         }
 
         /// <summary>